Timber structural members play an important part in the construction of building structures. Due to its strengths for load bearing and its natural ability to withstand a variety of forces, timber is commonly used for a variety of structures and sub-structures such as, for example, joists, beams, columns, rafters and frames. Further, when compared to metal based materials timber structural members are often less costly and are more easily cut and processed for specific building requirements.
There are, however, a number of disadvantages and complications associated with timber structural members. Any imperfection in a timber can compromise the strength of the member and, consequently, any structure built using that member. Accordingly, relatively high quality lumber is required for the manufacture of timber members (which include, for example, timber joists). This places a large demand on particular species of trees that are of specific age and quality, which in turn leads to increased cost in production as well as raising natural resource conservation issues. Depending on the part of the log solid timber is sawn from, the timber may have deficiencies or issues with splinters, rotting, knots, abnormal growth and grain structures. Additionally, when sawn and prepared for commercial use the lumbers are prone to processing defects such as chipping, torn grain and timber wanes.
Furthermore, using solid timber has the added difficulty that timber with appropriate dimensions and strength to weight ratio for a required application must be found. As will be appreciated, this is dependent on being able to find the appropriately sized and shaped tree from which the timber will be cut.
To address the problems associated with solid wood lumber, alternative forms of wood material for making timber joists have been sought. These include engineered wood composites such as plywood, laminated veneer lumber (“LVL”), oriented strand lumber (“OSL”) and oriented strand board (“OSB”). Wood composites have the advantage of being less expensive in raw material cost (as they are able to be formed from lower grade wood or even wood wastes) and do not have the problems associated with solid lumber defects. However, the energy and resource requirements in the manufacture of engineered wood composites are generally higher as processed structural timber requires more cutting, bonding and curing than naturally formed timber.
Timber joists made from wood composites are also problematic with respect to joining. They are usually joined by bearing onto another member and are nailed to deter sideway twisting and/or movement. For the joists to be able to withstand both axial compression and transverse bending, for example when used as beam/columns, additional torsion restraints are required such as noggins or end blockings. These torsion restraints can become design hindrances, for example when mounted metal braces are used. Additionally, metal braces are prone to oxidation and collapse in fire as their strength decreases significantly at elevated temperatures.
Accordingly, it would be desirable to provide a timber structural member that ameliorates or overcomes one or more of the above deficiencies or at least provides a useful alternative.
Reference to any prior art in the specification is not, and should not be taken as, an acknowledgment or any form of suggestion that this prior art forms part of the common general knowledge in Australia or any other jurisdiction or that this prior art could reasonably be expected to be ascertained, understood and regarded as relevant by a person skilled in the art.